generic/050: fix ro blockdev mount of xfs with quota
In XFS, mounting with quota always require a writable device. If
the block device is read only, the mount fails, which fails this
test. Since this is expected, work around this by simulating the
golden output when we expect a mount failure.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Eryu Guan <guaneryu@gmail.com> Signed-off-by: Eryu Guan <guaneryu@gmail.com>